Pharmaceutical composition for treatment and/or prophylaxis of cancer

ABSTRACT

This invention provides an antibody targeting a cancer antigenic protein specifically expressed on the surface of cancer cells and use thereof as a therapeutic and/or preventive agent for cancer. More specifically, the present invention provides an antibody, or a fragment thereof which has immunological reactivity with a CAPRIN-1 protein, the antibody comprising a heavy chain variable region comprising complementarity determining regions of SEQ ID NOs: 5, 6, and 7 and a light chain variable region comprising complementarity determining regions of SEQ ID NOs: 9, 10, and 11, and a pharmaceutical composition for treatment and/or prevention of cancer, comprising the same as an active ingredient.

TECHNICAL FIELD

The present invention relates to novel use of an antibody against CAPRIN-1 or a fragment thereof in a drug such as a therapeutic and/or preventive agent for cancer.

BACKGROUND ART

Cancer is the leading cause of death. This disease is currently treated principally by surgical therapy, in combination with radiation therapy and/or chemotherapy. In spite of recent development of novel surgical techniques or discovery of novel anticancer agents, the existing treatment of cancer has an insufficiently improved outcome, except for some cancer types. With recent advances of molecular biology or cancer immunology, antibodies that specifically react with cancer, cancer antigens that are recognized by cytotoxic T cells, genes encoding such cancer antigens, and the like have been identified, raising expectations on specific cancer therapy targeting the cancer antigens (Non Patent Literature 1).

For reducing the adverse reaction of cancer therapy, it is desired that peptides, polypeptides, or proteins recognized as antigens of the cancer should rarely exist in normal cells and specifically exist in cancer cells. In 1991, Boon et al. (Ludwig Institute for Cancer Research, Belgium) isolated a human melanoma antigen MAGE1 recognized by CD8-positive T cells by a cDNA expression cloning method using autologous cancer cell lines and cancer-reactive T cells (Non Patent Literature 2). Then, a SEREX (serological identification of antigens by recombinant expression cloning) method has been reported, which adopts a gene expression cloning approach to identify tumor antigens recognized by antibodies produced in response to autologous cancer in vivo in a cancer patient (Non Patent Literature 3 and Patent Literature 1). According to this method, some cancer antigens that are rarely expressed in normal cells and are specifically expressed in cancer have been isolated (Non Patent Literatures 4 to 9). In addition, cell therapy using immunocytes that specifically react with cancer antigens or cancer-specific immunotherapy using vaccines or the like comprising cancer antigens is under clinical trial targeting some of the isolated cancer antigens.

In recent years, various antibody drugs for cancer treatment targeting antigenic proteins on cancer cells have emerged in the world. These drugs have received attention because of their certain efficacy as cancer-specific therapeutic agents. A large majority of antigenic proteins targeted by the drugs, however, are also expressed in normal cells. As a result of administering the antibodies, cancer cells as well as normal cells expressing the antigens are damaged, disadvantageously resulting in adverse reaction. Thus, if cancer antigens specifically expressed on the surface of cancer cells can be identified and antibodies targeting the antigens can be used as drugs, these antibody drugs can be expected to achieve treatment with less adverse reaction.

Cytoplasmic- and proliferation-associated protein 1 (CAPRIN-1) has been known as an intracellular protein that is expressed upon activation or cell division of resting normal cells and forms cytoplasmic stress granules with RNAs in cells to participate in the regulation of transport and translation of mRNAs. This protein has been found to be specifically expressed on the surface of cancer cells and is therefore under study as a target of antibody drugs for cancer treatment (Patent Literature 2).

CITATION LIST Patent Literature

-   Patent Literature 1: U.S. Pat. No. 5,698,396 -   Patent Literature 2: WO2010/016526

Non Patent Literature

-   Non Patent Literature 1: Tsuyoshi Akiyoshi, “Japanese Journal of     Cancer and Chemotherapy”, 1997, Vol. 24, p. 551-519 (Japanese     Journal of Cancer and Chemotherapy Publishers Inc., Japan) -   Non Patent Literature 2: Bruggen P. et al., Science, 254: 1643-1647     (1991) -   Non Patent Literature 3: Proc. Natl. Acad. Sci. USA, 92: 11810-11813     (1995) -   Non Patent Literature 4: Int. J. Cancer, 72: 965-971 (1997) -   Non Patent Literature 5: Cancer Res., 58: 1034-1041 (1998) -   Non Patent Literature 6: Int. J. Cancer, 29: 652-658 (1998) -   Non Patent Literature 7: Int. J. Oncol., 14: 703-708 (1999) -   Non Patent Literature 8: Cancer Res., 56: 4766-4772 (1996) -   Non Patent Literature 9: Hum. Mol. Gene. 6: 33-39, 1997

SUMMARY OF INVENTION Technical Problem

An object of the present invention is to produce an antibody which targets CAPRIN-1 specifically expressed on the surface of cancer cells and has better antitumor activity than conventional antibodies, and provide use of the antibody as a therapeutic and/or preventive agent for cancer.

Solution to Problem

The present invention has the following aspects:

The present invention provides an antibody or a fragment thereof which has immunological reactivity with a CAPRIN-1 protein, wherein the antibody or the fragment thereof comprises a heavy chain variable region comprising complementarity determining regions of SEQ ID NOs: 5, 6, and 7 and a light chain variable region comprising complementarity determining regions of SEQ ID NOs: 9, 10, and 11, and a pharmaceutical composition for treatment and/or prevention of cancer, comprising the same as an active ingredient.

In one embodiment of the present invention, the cancer is breast cancer, kidney cancer, pancreatic cancer, colorectal cancer, lung cancer, brain tumor, gastric cancer, uterine cervix cancer, ovary cancer, prostate cancer, urinary bladder cancer, esophageal cancer, leukemia, lymphoma, fibrosarcoma, mastocytoma, or melanoma.

In an alternative embodiment, the antibody is a human antibody, a humanized antibody, a chimeric antibody, a single-chain antibody, or a multispecific antibody (e.g. bispecific antibody).

The present specification includes the contents disclosed in Japanese Patent Application No. 2011-171332 to which the present application claims priority.

Advantageous Effects of Invention

The antibody against CAPRIN-1 according to the present invention damages cancer cells. Thus, the antibody against CAPRIN-1 is useful in the treatment and/or prevention of cancer.

DESCRIPTION OF EMBODIMENTS

The antibody against CAPRIN-1 according to the present invention may be a monoclonal antibody or a polyclonal antibody and is preferably a monoclonal antibody. The antibody against CAPRIN-1 according to the present invention may be any type of antibody that can exert antitumor activity and includes, for example, recombinant antibodies, for example, synthetic antibodies, multispecific antibodies (e.g., bispecific antibodies), humanized antibodies, chimeric antibodies, and single-chain antibodies (scFv), human antibodies, and their antibody fragments, for example, Fab, F(ab′)₂, and Fv. These antibodies and fragments thereof can be prepared by methods generally known to those skilled in the art. In the case of a human subject, a human antibody or a humanized antibody is desirable for avoiding or suppressing rejection.

In this context, the phrase “specifically binding to the CAPRIN-1 protein” means that the antibody specifically binds to the CAPRIN-1 protein without substantially binding to other proteins.

The antibody against CAPRIN-1 polypeptide according to the present invention can be examined for its antitumor activity, as described later, by examining in vivo the inhibition of tumor growth in a cancer-bearing animal or by examining ex vivo the presence or absence of immunocyte- or complement-mediated cytotoxic activity exhibited by the antibody against tumor cells expressing the polypeptide.

The subject to receive the treatment and/or prevention of cancer according to the present invention is a mammal such as a human, a pet animal, livestock, or a sport animal, preferably a human.

Hereinafter, the present invention will be described in more detail.

<Preparation of Antigen for Antibody Preparation>

Proteins or fragments thereof used as sensitizing antigens for obtaining the antibody against CAPRIN-1 according to the present invention are not limited by animal species serving as their origins, including humans, dogs, cattle, horses, mice, rats, and chickens. The proteins or the fragments thereof; however, are preferably selected in view of compatibility with parent cells for use in cell fusion. In general, mammal-derived proteins are preferred. Particularly, human-derived proteins are preferred. For example, when CAPRIN-1 is human CAPRIN-1, human CAPRIN-1 proteins, partial peptides thereof, or cells expressing human CAPRIN-1 can be used.

The nucleotide sequences and amino acid sequences of human CAPRIN-1 and homologs thereof are available, for example, by accessing GenBank (NCBI, USA) and using BLAST or FASTA algorithm (Karlin and Altschul, Proc. Natl. Acad. Sci. USA, 90: 5873-5877, 1993; and Altschul et al., Nucleic Acids Res. 25: 3389-3402, 1997).

In the present invention, with reference to the nucleotide sequence (SEQ ID NO: 1 or 3) or amino acid sequence (SEQ ID NO: 2 or 4) of human CAPRIN-1, the target CAPRIN-1 is nucleic acids or proteins consisting of sequences having 70% to 100%, preferably 80% to 100%, more preferably 90% to 100%, further preferably 95% to 100%, for example, 97% to 100%, 98% to 100%, 99% to 100%, or 99.5% to 100% sequence identity to the nucleotide sequence or amino acid sequence of the ORF or mature portion of the reference sequence. In this context, the term “% sequence identity” means a percentage (%) of the number of identical amino acids (or nucleotide bases) to the total number of amino acids (or nucleotide bases) when two sequences are aligned such that the maximum degree of similarity (or identity) can be achieved with or without introduced gaps.

As the fragments of each CAPRIN-1 protein, those comprising an epitope (or an antigenic determinant), which is the smallest unit recognized by an antibody, and having lengths ranging from the amino acid length of the epitope, to less than the full-length of the protein can be used. The epitope refers to a polypeptide fragment having antigenicity or immunogenicity in mammals, preferably humans. Its smallest unit consists of approximately 7 to 12 amino acids, for example, 8 to 11 amino acids.

Polypeptide fragments comprising the above human CAPRIN-1 proteins and partial peptides thereof can be synthesized according to chemical synthesis methods, for example, Fmoc (fluorenylmethyloxycarbonyl) and tBoc (t-butyloxycarbonyl) methods (Seikagaku Jikken Koza (Biochemical Experimentation Course in English) 1, the Japanese Biochemical Society ed., Protein Chemistry IV, Chemical Modification and Peptide Synthesis, Tokyo Kagaku Dojin Co., Ltd. (Japan), 1981). Also, these polypeptides can be synthesized by conventional methods using various commercially available peptide synthesizers. Alternatively, polynucleotides encoding the polypeptides may be prepared using genetic engineering approaches known in the art (Sambrook et al., Molecular Cloning, the 2nd edition, Current Protocols in Molecular Biology (1989), Cold Spring Harbor Laboratory Press; Ausubel et al., Short Protocols in Molecular Biology, the 3rd edition, A compendium of Methods from Current Protocols in Molecular Biology (1995), John Wiley & Sons; etc.) and incorporated into expression vectors, which are then introduced into host cells to produce the polypeptides in the host cells. In this way, the human CAPRIN-1 proteins or polypeptide fragments thereof of interest can be obtained.

The polynucleotides encoding the polypeptides can be readily prepared by genetic engineering approaches known in the art or conventional methods using commercially available nucleic acid synthesizers. For example, a DNA comprising the nucleotide sequence of human CAPRIN-1 gene can be prepared by PCR using a human chromosomal DNA or cDNA library as a template and a pair of primers designed so as to be capable of amplifying the nucleotide sequence shown in SEQ ID NO: 1. Reaction conditions for this PCR can be appropriately determined. Examples of the conditions can include, but not limited to, 30 cycles each involving reaction steps consisting of 94° C. for 30 seconds (denaturation), 55° C. for 30 seconds to 1 minute (annealing), and 72° C. for 2 minutes (elongation) using thermostable DNA polymerase (e.g., Taq polymerase, Pfu polymerase or the like) and a Mg²⁺-containing PCR buffer, followed by reaction at 72° C. for 7 minutes. The PCR approach, conditions, etc. are described in, for example, Ausubel et al., Short Protocols in Molecular Biology, the 3rd edition, A Compendium of Methods from Current Protocols in Molecular Biology (1995), John Wiley & Sons (particularly, Chapter 15).

Also, appropriate probes or primers can be prepared on the basis of information about the nucleotide sequences of CAPRIN-1 gene and the amino acid sequences of CAPRIN-1 proteins, and used in the screening of, for example, a human cDNA library, to isolate the desired DNA. Preferably, such a cDNA library is produced from cells, organs, or tissues expressing CAPRIN-1 proteins. Examples of such cells or tissues include cells or tissues derived from the testis or from cancers or tumors such as leukemia, breast cancer, lymphoma, brain tumor, lung cancer, pancreatic cancer, and colorectal cancer. These operations, including the preparation of probes or primers, the construction of a cDNA library, the screening of the cDNA library, and the cloning of the gene of interest, are known to those skilled in the art and can be performed according to methods described in, for example, Sambrook et al., Molecular Cloning, the 2nd edition, Current Protocols in Molecular Biology (1989), and Ausubel et al. (ibid.). DNAs encoding the human CAPRIN-1 proteins and the partial peptides thereof can be obtained from the DNA thus obtained.

The host cells into which the expression vectors are introduced may be any cell capable of expressing the above polypeptides. Examples of prokaryotic cells include, but not limited to, E. coli. Examples of eukaryotic cells include, but not limited to: mammalian cells such as monkey kidney cells COS1 and Chinese hamster ovary cells CHO; a human embryonic kidney cell line HEK293; mouse embryonic skin cell line NIH3T3; yeast cells such as budding yeast and fission yeast cells; silkworm cells; and Xenopus egg cells.

In the case of using prokaryotic cells as the host cells, the expression vectors used may have an origin that permits replication in the prokaryotic cells, a promoter, a ribosomal binding site, a multicloning site, a terminator, a drug resistance gene, an auxotrophic complementary gene, etc. Examples of expression vectors for E. coli can include pUC series, pBluescript II, pET expression systems, and pGEX expression systems. The DNAs encoding the above polypeptides can be incorporated into such expression vectors, with which prokaryotic host cells are then transformed, followed by culture of the obtained transformants so that the polypeptides encoded by the DNAs are expressed in the prokaryotic host cells. In this respect, the polypeptides may be expressed as fusion proteins with other proteins.

In the case of using eukaryotic cells as the host cells, expression vectors for eukaryotic cells having a promoter, a splicing region, a poly(A) addition site, etc. may be used as the expression vectors. Examples of such expression vectors can include pKA1, pCDM8, pSVK3, pMSG, pSVL, pBK-CMV, pBK-RSV, EBV, pRS, pcDNA3, and pYES2 vectors. In the same way as above, the DNAs encoding the above polypeptides can be incorporated into such expression vectors, with which eukaryotic host cells are then transformed, followed by culture of the obtained transformants so that the polypeptides encoded by the DNAs are expressed in the eukaryotic host cells. In the case of using expression vectors such as pIND/V5-His, pFLAG-CMV-2, pEGFP-N1, or pEGFP-C1, the polypeptides may be expressed as various fusion proteins tagged with His tag (e.g., (His)₆ to (His)₁₀), FLAG tag, myc tag, HA tag, GFP, or the like.

The expression vectors can be introduced into the host cells using well known methods such as electroporation, a calcium phosphate method, a liposome method, a DEAE dextran method, microinjection, viral infection, lipofection, and binding with cell-penetrating peptides.

The polypeptide of interest can be isolated and purified from the host cells by a combination of separation operations known in the art. Examples thereof include, but not limited to, treatment with a denaturant (e.g., urea) or a surfactant, ultrasonication, enzymatic digestion, salting-out, solvent fractionation and precipitation, dialysis, centrifugation, ultrafiltration, gel filtration, SDS-PAGE, isoelectric focusing electrophoresis, ion-exchange chromatography, hydrophobic chromatography, affinity chromatography, and reverse-phase chromatography.

In order to prepare the antibody according to the present invention, antigens thus prepared can be used as sensitizing antigens as described later.

<Structure of Antibody>

Antibodies (immunoglobulin) are usually heteromultimeric glycoproteins each comprising at least two heavy chains and two light chains. The immunoglobulins, except for IgM, are heterotetrameric glycoproteins of approximately 150 kDa each composed of two identical light (L) chains and two identical heavy (H) chains. Typically, each light chain is connected to a heavy chain via a single covalent disulfide bond, though the number of disulfide bonds between heavy chains varies among different immunoglobulin isotypes. Each of the heavy and light chains also has an intrachain disulfide bond. Each heavy chain has a variable domain (VH region) at one end, followed by a series of constant regions. Each light chain has a variable domain (VL region) at one end and has a single constant region at the other end. The light chain constant region is aligned with the first heavy chain constant region, while the light chain variable domain is aligned with the heavy chain variable domain. Particular regions called complementarity determining regions (CDRs) in the antibody variable domains exhibit specific variability and impart binding specificity to the antibody. Portions relatively conserved in the variable regions are called framework regions (FRs). The complete heavy and light chain variable domains each comprise four FRs connected via three CDRs. These three CDRs are called CDRH1, CDRH2, and CDRH3 in this order from the N-terminus of the heavy chain. Likewise, the CDRs are called CDRL1, CDRL2, and CDRL3 in the light chain. CDRH3 is most important for the binding specificity of the antibody for its antigen. In addition, CDRs in each chain are kept close to each other by the FR regions and contribute to the formation of an antigen-binding site in the antibody, together with CDRs in the other chain. The constant regions do not directly contribute to antibody-antigen binding, but exhibit various effector functions, for example, involvement in antibody-dependent cellular cytotoxicity (ADCC), phagocytosis mediated by binding to an Fcy receptor, half-life/clearance rate mediated by a neonatal Fc receptor (FcRn), and complement-dependent cytotoxicity (CDC) mediated by a Clq component in the complement cascade.

<Preparation of Antibody>

The anti-CAPRIN-1 antibody according to the present invention means an antibody having immunological reactivity with a full-length CAPRIN-1 protein or a fragment thereof.

In this context, the “immunological reactivity” means the property of the antibody binding to the CAPRIN-1 antigen (a full-length CAPRIN-1 protein or a partial polypeptide thereof) in vivo. Via such binding of the antibody of the present invention to the CAPRIN-1, the antibody exerts the function of damaging (e.g., killing, suppressing, or regressing) tumor cells. The antibody of the present invention can damage tumors such as breast cancer, kidney cancer, pancreatic cancer, colorectal cancer, lung cancer, brain tumor, gastric cancer, uterine cervix cancer, ovary cancer, prostate cancer, urinary bladder cancer, esophageal cancer, leukemia, lymphoma, fibrosarcoma, mastocytoma, or melanoma as a result of binding to the CAPRIN-1 protein.

Preferably, the antibody of the present invention is not particularly limited as long as the antibody is monoclonal antibodies, and examples thereof include synthetic antibodies, multispecific antibodies, human antibodies, humanized antibodies, chimeric antibodies, single-chain antibodies, and antibody fragments (e.g., Fab, F(ab′)₂, and Fv). Also, the antibody is any class of immunoglobulin molecule, for example, IgG, IgE, IgM, IgA, IgD, or IgY, or any subclass, for example, IgG1, IgG2, IgG3, IgG4, IgA1, or IgA2.

Further, the antibody may be modified by acetylation, formylation, amidation, phosphorylation, PEGylation, or the like, as well as glycosylation.

Hereinafter, preparation examples of various monoclonal antibodies will be shown.

For example, breast cancer cell lines SK-BR-3 expressing CAPRIN-1 is administered to each mouse for immunization. The spleen is extracted from this mouse. After separation of spleen cells, the cells are fused with mouse myeloma cells. Clones producing antibodies having a cancer cell growth inhibitory effect are selected from among the obtained fusion cells (hybridomas). The hybridomas producing monoclonal antibodies having a cancer cell growth inhibitory effect are isolated and cultured. The antibody of the present invention can be prepared by purification from the culture supernatant according to a general affinity purification method.

The monoclonal antibody-producing hybridomas may be prepared, for example, as follows. First, animals are immunized with sensitizing antigens according to a method known in the art. This immunization method generally involves intraperitoneally or subcutaneously injecting the sensitizing antigens to mammals. Specifically, the sensitizing antigens are diluted with or suspended in PBS (phosphate-buffered saline), physiological saline, or the like into an appropriate amount and then mixed, if desired, with an appropriate amount of a conventional adjuvant, for example, a complete Freund's adjuvant. After emulsification, it is administered to each mammal several times every 4 to 21 days. Alternatively, an appropriate carrier may be used for the immunization with sensitizing antigens.

After confirmation of a rise in the level of the desired antibody in the serum of the mammal thus immunized, immunocytes are collected from the mammal and subjected to cell fusion. Preferred examples of the immunocytes particularly include spleen cells.

Mammalian myeloma cells are used as partner parent cells to be fused with the immunocytes. Various cell lines known in the art, for example, P3U1 (P3-X63Ag8U1), P3 (P3x63Ag8.653) (J. Immunol. (1979) 123, 1548-1550), P3x63Ag8U.1 (Current Topics in Microbiology and Immunology (1978) 81, 1-7), NS-1 (Kohler. G. and Milstein, C. Eur. J. Immunol. (1976) 6, 511-519), MPC-11 (Margulies. D. H. et al., Cell (1976) 8, 405-415), SP2/0 (Shulman, M. et al., Nature (1978) 276, 269-270), FO (deSt. Groth, S. F. et al., J. Immunol. Methods (1980) 35, 1-21), S194 (Trowbridge, I. S. J. Exp. Med. (1978) 148, 313-323), and R210 (Galfre, G. et al., Nature (1979) 277, 131-133), are preferably used as the myeloma cells.

The cell fusion between the immunocytes and the myeloma cells can be performed basically according to a method known in the art, for example, the method of Kohler and Milstein (Kohler, G. and Milstein, C. Methods Enzymol. (1981) 73, 3-46).

More specifically, the cell fusion is carried out, for example, in the presence of a cell fusion promoter in a conventional nutrient medium. For example, polyethylene glycol (PEG) or hemagglutinating virus of Japan (HVJ) is used as the fusion promoter. If desired, an auxiliary such as dimethyl sulfoxide may be further added in order to enhance fusion efficiency.

The ratio between the immunocytes and the myeloma cells used can be arbitrarily set. For example, the amount of the immunocytes is preferably set to 1 to 10 times the amount of the myeloma cells. Examples of the medium that can be used in the cell fusion include RPMI1640 and MEM media suitable for the growth of the myeloma cell lines as well as conventional media for use in this type of cell culture. In addition, a serum supplement such as fetal calf serum (FCS) may be used in combination with these cells.

For the cell fusion, the immunocytes and the myeloma cells are well mixed in a predetermined amount of the medium. A PEG solution (average molecular weight: for example, approximately 1000 to 6000) preheated to approximately 37° C. is usually added to the mixture at a concentration of 30 to 60% (w/v) and mixed therewith to form the hybridomas of interest. Subsequently, procedures of sequentially adding an appropriate medium and removing the supernatant by centrifugation are preferably repeated to remove cell fusion agents or the like unfavorable for the growth of the hybridomas.

The hybridomas thus obtained are cultured in a conventional selective medium, for example, a HAT medium (medium containing hypoxanthine, aminopterin, and thymidine) for selection. Culture in the HAT medium is continued for a period (usually, several days to several weeks) sufficient for the death of cells (non-fused cells) other than the hybridomas of interest. Subsequently, hybridomas producing the antibody of interest are screened for and cloned as single clones by a conventional limiting dilution method.

In addition to such obtainment of the hybridomas by the immunization of non-human animals with antigens, hybridomas producing human antibodies having the desired activity (e.g., cell growth inhibitory activity) may be obtained by sensitizing human lymphocytes, for example, EB virus-infected human lymphocytes, with proteins, protein-expressing cells, or lysates thereof in vitro and fusing the sensitized lymphocytes with human-derived myeloma cells capable of dividing permanently, for example, U266 (Accession No. TIB 196).

The monoclonal antibody-producing hybridomas thus prepared can be subcultured in a conventional medium and can also be stored for a long period in liquid nitrogen.

Specifically, the desired antigens or cells expressing the desired antigens are used as sensitizing antigens in immunization according to a conventional immunization method. The obtained immunocytes are fused with parent cells known in the art according to a conventional cell fusion method. Monoclonal antibody-producing cells (hybridomas) can be screened for by a conventional screening method to prepare the hybridomas producing monoclonal antibodies of interest.

In this context, for example, KM mice (Kirin Pharma Co., Ltd./Medarex) and Xeno mice (Amgen Inc.) are known as the human antibody-producing mice (e.g., International Publication Nos. WO02/43478 and WO02/092812). Complete human polyclonal antibodies can be obtained from the blood of such mice immunized with CAPRIN-1 proteins or fragments thereof. Alternatively, spleen cells may be isolated from the mice thus immunized and fused with myeloma cells. In this way, human monoclonal antibodies can be obtained.

The antigens can be prepared according to, for example, a method using animal cells (JP Patent Publication (Kohyo) No. 2007-530068 A (2007)) or a method using baculovirus (e.g., International Publication No. WO98/46777). Antigens having low immunogenicity can be bound to immunogenic macromolecules such as albumin for immunization. Antigens may be administered with adjuvants for immunization.

Alternatively, the antibody of the present invention may be obtained as recombinant antibodies, which are produced using a genetic engineering technique which involves: cloning the antibody genes from hybridomas; incorporating the antibody genes into appropriate vectors; and introducing the vectors into hosts (see, e.g., Carl, A. K. Borrebaeck, James, W. Larrick, THERAPEUTIC MONOCLONAL ANTIBODIES, Published in the United Kingdom by MACMILLAN PUBLISHERS LTD, 1990). Specifically, antibody variable region (V region) cDNAs are synthesized from the mRNAs of hybridomas using reverse transcriptase. After obtainment of DNAs encoding the antibody V regions of interest, the DNAs are ligated with DNAs encoding the desired antibody constant regions (C regions). The resulting ligation products are incorporated into expression vectors. Alternatively, the antibody V region-encoding DNAs may be incorporated into expression vectors containing antibody C region DNAs. These DNAs are incorporated into the expression vectors so as to be expressed under the control of expression control regions, for example, an enhancer and a promoter. Next, host cells can be transformed with the resulting expression vectors and allowed to express antibodies.

The anti-CAPRIN-1 antibody of the present invention is a monoclonal antibody. The monoclonal antibody includes human monoclonal antibodies, non-human animal monoclonal antibodies (e.g., mouse, rat, rabbit, and chicken monoclonal antibodies), chimeric monoclonal antibodies, and the like. The monoclonal antibody may be prepared by the culture of hybridomas obtained by the fusion between spleen cells from non-human animals (e.g., mice or human antibody-producing mice, chickens, and rabbits) immunized with CAPRIN-1 proteins or fragments thereof and myeloma cells. The chimeric antibody is an antibody prepared from a combination of sequences derived from different animals and is, for example, an antibody composed of mouse antibody heavy and light chain variable regions and human antibody heavy and light chain constant regions. The chimeric antibody can be prepared using a method known in the art which involves, for example: ligating DNAs encoding the antibody V regions with DNAs encoding human antibody C regions; incorporating the resulting ligation products into expression vectors; and introducing the vectors into hosts so that antibodies are produced.

Human-mouse chimeric monoclonal antibodies having an antitumor effect are prepared by a method described later in Examples. The monoclonal antibodies comprise, for example, a heavy chain variable (VH) region having the amino acid sequence of SEQ ID NO: 8 and a light chain variable (VL) region having the amino acid sequence of SEQ ID NO: 12. In the monoclonal antibodies, the VH region can comprise CDR1 shown by the amino acid sequence of SEQ ID NO: 5, CDR2 shown by the amino acid sequence of SEQ ID NO: 6, and CDR3 shown by the amino acid sequence of SEQ ID NO: 7, and the VL region can comprise CDR1 shown by the amino acid sequence of SEQ ID NO: 9, CDR2 shown by the amino acid sequence of SEQ ID NO: 10, and CDR3 shown by the amino acid sequence of SEQ ID NO: 11.

The humanized antibody, also called reshaped human antibody, is an engineered antibody. The humanized antibody is constructed by grafting antibody CDRs derived from an immunized animal into the complementarity determining regions of a human antibody. A general gene recombination approach therefor is also known.

Specifically, for example, DNA sequences designed so as to link mouse and chicken antibodies CDRs and human antibody framework regions (FRs) are synthesized by PCR using several prepared oligonucleotides having terminal portions overlapping with each other. The obtained DNAs are ligated with DNAs encoding human antibody constant regions. Subsequently, the resulting ligation products are incorporated into expression vectors, which are then introduced into hosts for antibody production to obtain the antibody of interest (see European Patent Application Publication No. EP239400 and International Publication No. WO96/02576). The human antibody FRs connected via CDRs are selected such that the complementarity determining regions form a favorable antigen-binding site. If necessary, amino acids in the framework regions of antibody variable regions may be substituted such that the complementarity determining regions of the resulting reshaped human antibody form an appropriate antigen-binding site (Sato K. et al., Cancer Research 1993, 53: 851-856). In addition, these framework regions may be replaced with framework regions derived from various human antibodies (see International Publication No. WO99/51743).

The human antibody framework regions connected via CDRs are selected such that the complementarity determining regions form a favorable antigen-binding site. If necessary, amino acids in the framework regions of antibody variable regions may be substituted such that the complementarity determining regions of the resulting reshaped human antibody form an appropriate antigen-binding site (Sato K. et al., Cancer Research 1993, 53: 851-856).

Amino acids in variable regions (e.g., FRs) or constant regions of the chimeric antibody or the humanized antibody thus prepared may be substituted, for example, by other amino acids.

The amino acid substitution is the substitution of, for example, less than 15, less than 10, 8 or less, 7 or less, 6 or less, 5 or less, 4 or less, 3 or less, or 2 or less amino acids, preferably 1 to 5 amino acids, more preferably 1 or 2 amino acids. The substituted antibody should be functionally equivalent to an unsubstituted antibody. The substitution is desirably conservative amino acid substitution, which is the substitution between amino acids similar in properties such as charge, side chains, polarity, and aromaticity. The amino acids can be classified in terms of similar properties into, for example: basic amino acids (arginine, lysine, and histidine); acidic amino acids (aspartic acid and glutamic acid); uncharged polar amino acids (glycine, asparagine, glutamine, serine, threonine, cysteine, and tyrosine); nonpolar amino acids (leucine, isoleucine, alanine, valine, proline, phenylalanine, tryptophan, and methionine); branched amino acids (threonine, valine, and isoleucine); and aromatic amino acids (phenylalanine, tyrosine, tryptophan, and histidine).

Examples of modified antibodies can include antibodies bound with various molecules such as polyethylene glycol (PEG). In the modified antibody of the present invention, the substance to be bound is not limited. In order to obtain such a modified antibody, the obtained antibody can be chemically modified. A method therefor has already been established in the art.

In this context, the phrase “functionally equivalent” means that an antibody concerned has biological or biochemical activity similar to that of the antibody of the present invention, specifically, the antibody concerned has the function of damaging tumor and essentially causes no rejection when applied to humans, for example. Examples of such activity can include cell growth inhibitory activity and binding activity.

A method for preparing a polypeptide functionally equivalent to a certain polypeptide, which involves introducing a mutation into a polypeptide, is well known to those skilled in the art. For example, those skilled in the art can introduce a mutation as appropriate into the antibody of the present invention using site-directed mutagenesis (Hashimoto-Gotoh, T. et al., (1995) Gene 152, 271-275; Zoller, M J., and Smith, M. (1983) Methods Enzymol. 100, 468-500; Kramer, W. et al., (1984) Nucleic Acids Res. 12, 9441-9456; Kramer, W. and Fritz, H J., (1987) Methods Enzymol. 154, 350-367; Kunkel, T A., (1985) Proc. Natl. Acad. Sci. USA. 82, 488-492; and Kunkel (1988) Methods Enzymol. 85, 2763-2766) or the like, thereby prepare an antibody functionally equivalent to the antibody of the present invention.

An antibody that recognizes an epitope of a CAPRIN-1 protein described above can be obtained by a method generally known to those skilled in the art. For example, the antibody can be obtained by a method which involves determining the epitope of the CAPRIN-1 protein recognized by the anti-CAPRIN-1 antibody having a cancer cell growth inhibitory effect obtained by the above by a conventional method (e.g., epitope mapping) and preparing an antibody using a polypeptide having an amino acid sequence contained in the epitope as an immunogen, or a method which involves determining an epitope for an antibody prepared by a conventional method and selecting an antibody that recognizes the same epitope as that for the anti-CAPRIN-1 antibody. In this context, the “epitope” refers to a polypeptide fragment having antigenicity or immunogenicity in mammals, preferably humans. Its smallest unit consists of approximately 7 to 12 amino acids, preferably 8 to 11 amino acids.

The antibody of the present invention is an antibody having immunological reactivity with CAPRIN-1, an antibody specifically recognizing CAPRIN-1, or an antibody specifically binding to CAPRIN-1 and exhibits cytotoxic activity or tumor growth inhibitory effect on cancer. The antibody preferably has a structure that causes little or no rejection in recipient animals. Examples of such antibodies include human antibodies, humanized antibodies, chimeric antibodies (e.g., human-mouse chimeric antibodies), single-chain antibodies, and bispecific antibodies when the recipient animals are humans. These antibodies have heavy and light chain variable regions derived from a human antibody or have heavy and light chain variable regions consisting of complementarity determining regions (CDR1, CDR2, and CDR3) derived from a non-human animal antibody and framework regions derived from a human antibody. Alternatively, these antibodies are recombinant antibodies having heavy and light chain variable regions derived from a non-human animal antibody and heavy and light chain constant regions derived from a human antibody. The antibody of the present invention is preferably the former two antibodies.

Such recombinant antibodies can be prepared as follows: DNAs encoding monoclonal antibodies (e.g., human, mouse, rat, rabbit, and chicken monoclonal antibodies) against human CAPRIN-1 are cloned from the antibody-producing cells such as hybridomas and used as templates to prepare DNAs encoding the light and heavy chain variable regions of the antibodies by RT-PCR or the like. The respective sequences of the light and heavy chain variable regions and the respective sequences of CDR1, CDR2, and CDR3 in each region are determined on the basis of the Kabat EU numbering system (Kabat et al., Sequences of Proteins of Immunological Interest, 5th Ed. Public Health Service, National Institute of Health, Bethesda, Md. (1991)).

A DNA encoding each variable region or a DNA encoding each CDR is prepared using a genetic engineering technique (Sambrook et al., Molecular Cloning A Laboratory Manual, Cold Spring Harbor Laboratory Press (1989)) or a DNA synthesizer. The above-mentioned human monoclonal antibody-producing hybridomas can be prepared by immunizing human antibody-producing animals (e.g., mice) with human CAPRIN-1 and then fusing spleen cells excised from the immunized animals with myeloma cells. Separately, DNAs encoding light or heavy chain variable and constant regions derived from a human antibody are prepared, if necessary, using a genetic engineering technique or a DNA synthesizer.

For the humanized antibody, a DNA encoding the humanized antibody can be prepared by producing DNAs in which the CDR coding sequences in DNAs encoding a human antibody-derived light or heavy chain variable regions are substituted by corresponding CDR coding sequences of a non-human animal (e.g., mouse, rat, rabbit, or chicken)-derived antibody, ligating the resulting DNAs with the DNAs encoding human antibody-derived light or heavy chain constant regions, respectively.

For the chimeric antibody, a DNA encoding the chimeric antibody can be prepared by ligating DNAs encoding light or heavy chain variable regions of a non-human animal (e.g., mouse, rat, rabbit, or chicken)-derived antibody with DNAs encoding human antibody-derived light or heavy chain constant regions.

The single-chain antibody means an antibody in which heavy and light chain variable regions are linearly linked to each other via a linker. A DNA encoding the single-chain antibody can be prepared by ligating a DNA encoding the heavy chain variable region, a DNA encoding the linker, and a DNA encoding the light chain variable region. In this context, the heavy and light chain variable regions are both derived from a human antibody or derived from a human antibody in which CDRs alone are substituted by CDRs of a non-human animal (e.g., mouse, rat, rabbit, or chicken)-derived antibody. The linker consists of 12 to 19 amino acids. Examples thereof include (G₄S)₃ consisting of 15 amino acids (G. B. Kim et al., Protein Engineering Design and Selection 2007, 20 (9): 425-432).

The bispecific antibody (diabody) means an antibody capable of specifically binding to two different epitopes. A DNA encoding the bispecific antibody can be prepared by, for example, ligating, for example, a DNA encoding a heavy chain variable region A, a DNA encoding a light chain variable region B, a DNA encoding a heavy chain variable region B, and a DNA encoding a light chain variable region A in this order, wherein the DNA encoding the light chain variable region B and the DNA encoding the heavy chain variable region B are ligated via a DNA encoding a linker as described above). In this context, the heavy and light chain variable regions are all derived from a human antibody or derived from a human antibody in which CDRs alone are substituted by CDRs of a non-human animal (e.g., mouse, rat, rabbit, or chicken)-derived antibody.

The recombinant DNAs thus prepared can be incorporated into one or more appropriate vectors, which are then introduced into host cells (e.g., mammalian cells, yeast cells, and insect cells), and the DNAs are (co)expressed to produce recombinant antibodies (see, P. J. Delves., ANTIBODY PRODUCTION ESSENTIAL TECHNIQUES., 1997 WILEY, P. Shepherd and C. Dean., Monoclonal Antibodies., 2000 OXFORD UNIVERSITY PRESS; and J. W. Goding., Monoclonal Antibodies: principles and practice., 1993 ACADEMIC PRESS).

Examples of the antibody of the present invention prepared by any of the methods described above include the following antibody (a) obtained in Examples described later:

(a) an antibody comprising a heavy chain variable region comprising complementarity determining regions of SEQ ID NOs: 5, 6, and 7 and a light chain variable region comprising complementarity determining regions of SEQ ID NOs: 9, 10, and 11 (e.g., an antibody having a heavy chain variable region of SEQ ID NO: 8 and a light chain variable region of SEQ ID NO: 12);

In this context, the amino acid sequences shown by SEQ ID NOs: 5, 6, and 7 correspond to CDR1, CDR2, and CDR3, respectively, of a mouse antibody-derived heavy chain variable region. The amino acid sequences shown by SEQ ID NOs: 9, 10, and 11 correspond to CDR1, CDR2, and CDR3, respectively, of a mouse antibody-derived light chain variable region.

Examples of the humanized antibody, the chimeric antibody, the single-chain antibody, or the bispecific antibody of the present invention include antibodies described below.

(i) an antibody comprising a heavy chain variable region comprising the amino acid sequences of SEQ ID NOs: 5, 6, and 7 and the amino acid sequences of human antibody-derived framework regions and a light chain variable region comprising the amino acid sequences of SEQ ID NOs: 9, 10, and 11 and the amino acid sequences of human antibody-derived framework regions.

(ii) an antibody comprising a heavy chain variable region comprising the amino acid sequences of SEQ ID NOs: 5, 6, and 7 and the amino acid sequences of human antibody-derived framework regions, a heavy chain constant region comprising a human antibody-derived amino acid sequence, a light chain variable region comprising the amino acid sequences of SEQ ID NOs: 9, 10, and 11 and the amino acid sequences of human antibody-derived framework regions, and a light chain constant region comprising a human antibody-derived amino acid sequence.

(iii) an antibody comprising a heavy chain variable region comprising the amino acid sequence of SEQ ID NO: 8, a heavy chain constant region comprising a human antibody-derived amino acid sequence, a light chain variable region comprising the amino acid sequence of SEQ ID NO: 12, and a light chain constant region comprising a human antibody-derived amino acid sequence.

The sequences of the constant and variable regions of human antibody heavy and light chains are available from, for example, NCBI (USA; GenBank, UniGene, etc.). For example, the following sequences can be referred to: Accession No. J00228 for a human IgG1 heavy chain constant region; Accession No. J00230 for a human IgG2 heavy chain constant region; Accession No. X03604 for a human IgG3 heavy chain constant region; Accession No. K01316 for a human IgG4 heavy chain constant region; Accession Nos. V00557, X64135, and X64133 for a human light chain κ constant region; and Accession Nos. X64132 and X64134 for a human light chain λ constant region.

Preferably, these antibodies have cytotoxic activity and can thereby exert an antitumor effect.

The above particular sequences of the heavy and light chain variable regions and CDRs in the above-mentioned antibodies are provided merely for illustrative purposes, and it is clear that the antibody of the present invention is not limited by the particular sequences. Hybridomas capable of producing anti-human CAPRIN-1 human antibodies or non-human animal antibodies (e.g., mouse antibodies) different from those specifically described above are prepared, and monoclonal antibodies produced by the hybridomas are recovered and it is determined whether or not the recovered antibodies are the antibodies of interest using the immunological binding activity against human CAPRIN-1 and cytotoxic activity as indicators. The monoclonal antibody-producing hybridomas of interest are thereby identified. Then, DNAs encoding heavy and light chain variable regions of the antibodies of interest are prepared from the hybridomas and sequenced, as described above. The DNAs are used for the preparation of different antibodies.

The antibody described above may be the antibody (a) having the substitution, deletion, or addition of one or several amino acids, in particular, in a framework region sequence and/or a constant region sequence, as long as the antibody has such specificity that it can specifically recognize CAPRIN-1. Herein, the term “several” preferably means 2 to 5, more preferably 2 or 3.

The antibody of the present invention has an affinity constant Ka (k_(on)/k_(off)) of preferably at least 10⁷ M⁻¹, at least 10⁸ M⁻¹, at least 5×10⁸ M⁻¹, at least 10⁹ M⁻¹, at least 5×10⁹ M⁻¹, at least 10¹⁰ M⁻¹, at least 5×10¹⁰ M⁻¹ at least 10¹¹ M⁻¹, at least 5×10¹¹ M⁻¹, at least 10¹² M⁻¹, or at least 10¹³ M⁻¹ for the CAPRIN-1 protein or the fragment thereof.

The antibody of the present invention can be conjugated with an antitumor agent. The conjugation of the antibody with the antitumor agent can be performed via a spacer having a group reactive with an amino group, a carboxyl group, a hydroxy group, a thiol group, or the like (e.g., a succinimidyl group, a formyl group, a 2-pyridyldithio group, a maleimidyl group, an alkoxycarbonyl group, or a hydroxy group).

Examples of the antitumor agent include the following antitumor agents known by literatures, etc.: paclitaxel, doxorubicin, daunorubicin, cyclophosphamide, methotrexate, 5-fluorouracil, thiotepa, busulfan, improsulfan, piposulfan, benzodopa, carboquone, meturedopa, uredopa, altretamine, triethylenemelamine, triethylenephosphoramide, triethylenethiophosphoramide, trimethylolomelamine, bullatacin, bullatacinone, camptothecin, bryostatin, callystatin, cryptophycin 1, cryptophycin 8, dolastatin, duocarmycin, eleutherobin, pancratistatin, sarcodictyin, spongistatin, chlorambucil, chlornaphazine, cholophosphamide, estramustine, ifosfamide, mechlorethamine, mechlorethamine oxide hydrochloride, melphalan, novembichin, phenesterine, prednimustine, trofosfamide, uracil mustard, carmustine, chlorozotocin, fotemustine, lomustine, nimustine, ranimustine, calicheamicin, dynemicin, clodronate, esperamicin, aclacinomycin, actinomycin, authramycin, azaserine, bleomycin, cactinomycin, carabicin, caminomycin, carzinophilin, chromomycin, dactinomycin, detorbicin, 6-diazo-5-oxo-L-norleucine, Adriamycin, epirubicin, esorubicin, idarubicin, marcellomycin, mitomycin C, mycophenolic acid, nogalamycin, olivomycin, peplomycin, potfiromycin, puromycin, quelamycin, rodorubicin, streptonigrin, streptozocin, tubercidin, ubenimex, zinostatin, zorubicin, denopterin, pteropterin, trimetrexate, fludarabine, 6-mercaptopurine, thiamiprine, thioguanine, ancitabine, azacitidine, 6-azauridine, carmofur, cytarabine, dideoxyuridine, doxifluridine, enocitabine, floxuridine, androgens (e.g., calusterone, dromostanolone propionate, epitiostanol, mepitiostane, and testolactone), aminoglutethimide, mitotane, trilostane, frolinic acid, aceglatone, aldophosphamide glycoside, aminolevulinic acid, eniluracil, amsacrine, bestrabucil, bisantrene, edatraxate, defofamine, demecolcine, diaziquone, elformithine, elliptinium acetate, epothilone, etoglucid, lentinan, lonidamine, maytansine, ansamitocin, mitoguazone, mitoxantrone, mopidanmol, nitraerine, pentostatin, phenamet, pirarubicin, losoxantrone, podophyllinic acid, 2-ethylhydrazide, procarbazine, razoxane, rhizoxin, schizophyllan, spirogermanium, tenuazonic acid, triaziquone, roridin A, anguidine, urethane, vindesine, dacarbazine, mannomustine, mitobronitol, mitolactol, pipobroman, gacytosine, docetaxel, chlorambucil, gemcitabine, 6-thioguanine, mercaptopurine, cisplatin, oxaliplatin, carboplatin, vinblastine, etoposide, ifosfamide, mitoxantrone, vincristine, vinorelbine, novantrone, teniposide, edatrexate, daunomycin, aminopterin, Xeloda, ibandronate, irinotecan, topoisomerase inhibitors, difluoromethylornithine (DMFO), retinoic acid, capecitabine, and pharmaceutically acceptable salts and derivatives thereof.

Alternatively, the antibody of the present invention can be administered in combination with an antitumor agent to produce a higher therapeutic effect. This approach is adaptable to a patient with a cancer expressing CAPRIN-1 either before or after surgical operation. This approach can be applied, particularly after surgery, to CAPRIN-1-expressing cancer, which has been treated conventionally with an antitumor agent alone, to produce higher prevention of cancer recurrence or prolongation of survival time.

Examples of the antitumor agent used in the combined administration with the antibody of the present invention include the following antitumor agents known by literatures, etc.: paclitaxel, doxorubicin, daunorubicin, cyclophosphamide, methotrexate, 5-fluorouracil, thiotepa, busulfan, improsulfan, piposulfan, benzodopa, carboquone, meturedopa, uredopa, altretamine, triethylenemelamine, triethylenephosphoramide, triethylenethiophosphoramide, trimethylolomelamine, bullatacin, bullatacinone, camptothecin, bryostatin, callystatin, cryptophycin 1, cryptophycin 8, dolastatin, duocarmycin, eleutherobin, pancratistatin, sarcodictyin, spongistatin, chlorambucil, chlornaphazine, cholophosphamide, estramustine, ifosfamide, mechlorethamine, mechlorethamine oxide hydrochloride, melphalan, novembichin, phenesterine, prednimustine, trofosfamide, uracil mustard, carmustine, chlorozotocin, fotemustine, lomustine, nimustine, ranimustine, calicheamicin, dynemicin, clodronate, esperamicin, aclacinomycin, actinomycin, authramycin, azaserine, bleomycin, cactinomycin, carabicin, caminomycin, carzinophilin, chromomycin, dactinomycin, detorbicin, 6-diazo-5-oxo-L-norleucine, Adriamycin, epirubicin, esorubicin, idarubicin, marcellomycin, mitomycin C, mycophenolic acid, nogalamycin, olivomycin, peplomycin, potfiromycin, puromycin, quelamycin, rodorubicin, streptonigrin, streptozocin, tubercidin, ubenimex, zinostatin, zorubicin, denopterin, pteropterin, trimetrexate, fludarabine, 6-mercaptopurine, thiamiprine, thioguanine, ancitabine, azacitidine, 6-azauridine, carmofur, cytarabine, dideoxyuridine, doxifluridine, enocitabine, floxuridine, calusterone, dromostanolone propionate, epitiostanol, mepitiostane, testolactone, aminoglutethimide, mitotane, trilostane, frolinic acid, aceglatone, aldophosphamide glycoside, aminolevulinic acid, eniluracil, amsacrine, bestrabucil, bisantrene, edatraxate, defofamine, demecolcine, diaziquone, elfornithine, elliptinium acetate, epothilone, etoglucid, lentinan, lonidamine, maytansine, ansamitocin, mitoguazone, mitoxantrone, mopidanmol, nitraerine, pentostatin, phenamet, pirarubicin, losoxantrone, podophyllinic acid, 2-ethylhydrazide, procarbazine, razoxane, rhizoxin, schizophyllan, spirogermanium, tenuazonic acid, triaziquone, roridin A, anguidine, urethane, vindesine, dacarbazine, mannomustine, mitobronitol, mitolactol, pipobroman, gacytosine, docetaxel, chlorambucil, gemcitabine, 6-thioguanine, mercaptopurine, cisplatin, oxaliplatin, carboplatin, vinblastine, etoposide, ifosfamide, mitoxantrone, vincristine, vinorelbine, novantrone, teniposide, edatrexate, daunomycin, aminopterin, Xeloda, ibandronate, irinotecan, topoisomerase inhibitors, difluoromethylornithine (DMFO), retinoic acid, capecitabine, and pharmaceutically acceptable salts (known in the art) and derivatives (known in the art) thereof. Of these antitumor agents, cyclophosphamide, paclitaxel, docetaxel, or vinorelbine is particularly preferably used.

The antibody of the present invention may be bound to a radioisotope known by literatures, etc., such as 211At, ¹³¹I, ¹²⁵I, ⁹⁰Y, ¹⁸⁶Re, ¹⁸⁸Re, ¹⁵³Sm, ²¹²Bi, ³²P, ¹⁷⁵Lu, or ¹⁷⁶Lu. Preferably, a radioisotope effective for the treatment or diagnosis of tumor is used. Such a radioisotope is also included in the scope of the antitumor agent according to the present invention.

<Antitumor Effect>

It is considered that the antitumor effect of the anti-CAPRIN-1 antibody to be used in the present invention on CAPRIN-1-expressing cancer cells is brought about by the following mechanism: Antibody-dependent effector cell-mediated cytotoxicity (ADCC) against the CAPRIN-1-expressing cancer cells and complement-dependent cytotoxicity (CDC) against the CAPRIN-1-expressing cells. However, the scope of the present invention is not intended to be limited by the mechanism.

The antitumor effect based on the mechanism is known to correlate with the number of antibody-binding target molecules expressed on the surface of cancer cells (Niwa R., Clinical Cancer Research (2005) Mar. 15; 11 (6): 2327-2336). The number of target molecules expressed on the surface of cancer cells can be examined using an existing assay kit capable of measuring the number of molecules on cell surface. Specifically, the number of antibody-binding target molecules can be determined by: reacting cancer cells with, for example, antibodies against the target molecules as primary antibodies; reacting therewith fluorescently labeled antibodies against the primary antibodies, together with calibration curve beads with the preliminarily known number of molecules; measuring the mean fluorescence intensity of the samples; and determining the number of the target molecules on the basis of the obtained calibration curve.

Thus, the anti-CAPRIN-1 antibody to be used in the present invention can be assayed for its activity by determining ex vivo the ADCC activity or the CDC activity against CAPRIN-1-expressing cancer cells or by examining the number of CAPRIN-1 molecules expressed on the surface of cancer cells in the case of using the anti-CAPRIN-1 antibody according to the present invention as a primary antibody as specifically shown below in Examples.

The anti-CAPRIN-1 antibody to be used in the present invention binds to CAPRIN-1 proteins on cancer cells and exhibits an antitumor effect through the activity. Thus, the anti-CAPRIN-1 antibody of the present invention is considered to be useful in the treatment or prevention of cancer. Specifically, the present invention provides a pharmaceutical composition for treatment and/or prevention of cancer, comprising the anti-CAPRIN-1 antibody as an active ingredient. The anti-CAPRIN-1 antibody to be used for the purpose of administration to human bodies (antibody therapy) is preferably a human antibody or a humanized antibody for reducing immunogenicity.

The anti-CAPRIN-1 antibody with higher binding affinity for a CAPRIN-1 protein on the surface of cancer cells exerts stronger antitumor activity. Thus, the antibody according to the present invention can be expected to have a stronger antitumor effect due to the high binding affinity for the CAPRIN-1 protein, and therefore it can be used as a pharmaceutical composition for use in the treatment and/or prevention of cancer. Preferably, the antibody according to the present invention has high binding affinity with association constant (affinity constant) Ka (k_(on)/k_(off)) of preferably at least 10⁷ M⁻¹, at least 10⁸ M⁻¹, at least 5×10⁸ M⁻¹, at least 10⁹ M⁻¹, at least 5×10⁹ M⁻¹, at least 10¹⁰ M⁻¹, at least 5×10¹⁰ M⁻¹ at least 10¹¹ M⁻¹, at least 5×10¹¹ M⁻¹, at least 10¹² M⁻¹, or at least 10¹³ M⁻¹, as described above.

A larger number of CAPRIN-1 molecules that can bind to anti-CAPRIN-1 antibodies on the surface of cancer cells produces stronger antitumor activity. Desirably, in order to produce the expected antitumor effect, the number of CAPRIN-1 molecules to which the antibodies bind is 10⁴ or more, preferably 10⁵ or more CAPRIN-1 molecules per cancer cell, as measured using the anti-CAPRIN-1 antibody of the present invention. Tumor (cancer cells) having a large number of CAPRIN-1 molecules on its cell surface is particularly preferred as cancer subject to the administration of the antibody of the present invention.

<Binding to Antigen-Expressing Cells>

The ability of the antibody to bind to CAPRIN-1 can be determined by use of binding assay using, for example, ELISA, Western blot, immunofluorescence, and flow cytometry analysis, as described in Examples.

<Immunohistochemical Staining>

The antibody that recognizes CAPRIN-1 can be tested for its reactivity with CAPRIN-1 by an immunohistochemical method well known to those skilled in the art using a paraformaldehyde- or acetone-fixed frozen section or paraformaldehyde-fixed paraffin-embedded tissue section of a tissue obtained from a patient during surgical operation or from a xenograft tissue-carrying animal inoculated with a cell line expressing CAPRIN-1 either spontaneously or after transfection.

For immunohistochemical staining, the antibody reactive with CAPRIN-1 can be stained by various methods. For example, the antibody can be visualized through reaction with a horseradish peroxidase-conjugated goat anti-mouse antibody, goat anti-rabbit antibody, or goat anti-chicken antibody.

<Pharmaceutical Composition, and Method for Treating and/or Preventing Cancer>

A target of the pharmaceutical composition for treatment and/or prevention of cancer of the present invention is not particularly limited as long as the target is cancer (cells) expressing a CAPRIN-1 gene.

The terms “tumor” and “cancer” used herein mean malignant neoplasm and are used interchangeably with each other.

The cancer targeted in the present invention is cancer expressing a CAPRIN-1 protein-encoding gene and is preferably breast cancer, kidney cancer, pancreatic cancer, colorectal cancer, lung cancer, brain tumor, gastric cancer, uterine cervix cancer, ovary cancer, prostate cancer, urinary bladder cancer, esophageal cancer, leukemia, lymphoma, fibrosarcoma, mastocytoma, or melanoma.

Specific examples of these cancers include, but not limited to, breast adenocarcinoma, complex-type breast adenocarcinoma, malignant mixed tumor of mammary gland, intraductal papillary adenocarcinoma, lung adenocarcinoma, squamous cell cancer, small-cell cancer, large-cell cancer, glioma which is tumor of neuroepithelial tissue, ventricular ependymoma, neuronal tumor, embryonal neuroectodermal tumor, neurilemmoma, neurofibroma, meningioma, chronic lymphocytic leukemia, lymphoma, gastrointestinal lymphoma, alimentary lymphoma, small to medium cell-type lymphoma, cecal cancer, ascending colon cancer, descending colon cancer, transverse colon cancer, sigmoid colon cancer, rectal cancer, epithelial ovarian cancer, germ cell tumor, stromal cell tumor, pancreatic ductal carcinoma, invasive pancreatic ductal carcinoma, pancreatic adenocarcinoma, acinar cell carcinoma, adenosquamous carcinoma, giant cell tumor, intraductal papillary-mucinous neoplasm, mucinous cystic neoplasm, pancreatoblastoma, serous cystadenocarcinoma, solid papillary tumor, gastrinoma, glucagonoma, insulinoma, multiple endocrine neoplasia type-1 (Wermer's syndrome), nonfunctional islet cell tumor, somatostatinoma, and VIPoma.

The subject (patient) as the recipient is preferably mammals, for example, mammals including primates, pet animals, livestock, and sport animals and particularly preferably humans, dogs, and cats.

When using the antibody of the present invention in a pharmaceutical composition, the pharmaceutical composition can be formulated by a method known to those skilled in the art. For example, the pharmaceutical composition can be used in the form of a parenteral injection of an aseptic solution or suspension with water or any other pharmaceutically acceptable liquid. For example, the pharmaceutical composition may be formulated with the antibody mixed in a unit dosage form required for generally accepted pharmaceutical practice, in combination with pharmacologically acceptable carriers or media, specifically, sterilized water, physiological saline, plant oil, an emulsifier, a suspending agent, a surfactant, a stabilizer, a flavoring agent, an excipient, a vehicle, a preservative, a binder, etc, as appropriate. The amount of the active ingredient in such a preparation is determined such that an appropriate dose within the indicated range can be achieved.

An aseptic composition for injection can be formulated according to conventional pharmaceutical practice using a vehicle such as injectable distilled water.

Examples of aqueous solutions for injection include physiological saline, isotonic solutions containing glucose and other adjuvants, for example, D-sorbitol, D-mannose, D-mannitol, and sodium chloride. These solutions may be used in combination with an appropriate solubilizer, for example, an alcohol (particularly, ethanol) or a polyalcohol (e.g., propylene glycol and polyethylene glycol), or a nonionic surfactant, for example, polysorbate 80 (TM) or HCO-60.

Examples of oily solutions include those using sesame oil or soybean oil. The solutions may be used in combination with a solubilizer such as benzyl benzoate or benzyl alcohol. A buffer (e.g., a phosphate buffer solution or a sodium acetate buffer solution), a soothing agent (e.g., procaine hydrochloride), a stabilizer (e.g., benzyl alcohol or phenol), or an antioxidant may be added to the solutions. The injection solutions thus prepared are generally charged into appropriate ampules.

The pharmaceutical composition of the present invention is administered orally or parenterally, preferably parenterally. Specific examples of its dosage forms include injections, intranasal administration agents, transpulmonary administration agents, and percutaneous administration agents. Examples of the injections include intravenous injection, intramuscular injection, intraperitoneal injection, and subcutaneous injection, through which the pharmaceutical composition can be administered systemically or locally.

Also, the administration method can be appropriately selected depending on the age, weight, sex, symptoms, etc. of a patient. The dose of a pharmaceutical composition containing the antibody or a polynucleotide encoding the antibody can be selected within a range of, for example, 0.0001 to 1000 mg/kg of body weight per dose. Alternatively, the dose can be selected within a range of, for example, 0.001 to 100000 mg/body of a patient, though the dose is not necessarily limited to these numeric values. Although the dose and the administration method vary depending on the weight, age, sex, symptoms, etc. of a patient, those skilled in the art can appropriately select the dose and the method.

The pharmaceutical composition including the antibody of the present invention or fragments thereof can be administered to a subject to treat and/or prevent cancer, preferably breast cancer, kidney cancer, pancreatic cancer, colorectal cancer, lung cancer, brain tumor, gastric cancer, uterine cervix cancer, ovary cancer, prostate cancer, urinary bladder cancer, esophageal cancer, leukemia, lymphoma, fibrosarcoma, mastocytoma, or melanoma.

The present invention further encompasses a method for treating and/or preventing cancer, comprising administering the pharmaceutical composition of the present invention in combination with the antitumor agent as exemplified above or a pharmaceutical composition comprising the antitumor agent to a subject. The antibody of the present invention or the fragment thereof may be administered simultaneously with or separately from the antitumor agent to the subject. In the case of separately administering these pharmaceutical compositions, either one may be administered first or later. Their dosing intervals, doses, administration routes, and the number of doses can be appropriately selected by a specialist. The other pharmaceutical dosage forms to be administered simultaneously also include, for example, pharmaceutical compositions formulated by mixing the antibody of the present invention or the fragment thereof or the antitumor agent into a pharmacologically acceptable carrier (or medium). The above descriptions about composition, formulation, administration routes, doses, cancer, etc. as to the pharmaceutical compositions and dosage forms containing the antibody of the present invention are also applicable to any of the above-mentioned pharmaceutical compositions and dosage forms containing the antitumor agent.

Thus, the present invention also provides a pharmaceutical combination for treatment and/or prevention of cancer, comprising the pharmaceutical composition of the present invention and a pharmaceutical composition comprising the antitumor agent as exemplified above. The present invention also provides a pharmaceutical composition for treatment and/or prevention of cancer, comprising the antibody or the fragment thereof of the present invention and the antitumor agent together with a pharmacologically acceptable carrier.

<Polypeptide and DNA>

The present invention further provides a DNA encoding the antibody of the present invention or the fragment (antibody-binding fragment) thereof. The DNA may be a DNA encoding the heavy and/or light chains of the antibody or may be a DNA encoding the heavy and/or light chain variable regions of the antibody. The DNA may also be a DNA encoding each or a combination of the complementarity determining regions of antibody. Such a DNA includes, for example, a heavy chain variable region-encoding DNA comprising nucleotide sequences encoding the amino acid sequences of SEQ ID NOs: 5, 6, and 7, and a light chain variable region-encoding DNA comprising nucleotide sequences encoding the amino acid sequences of SEQ ID NOs: 9, 10, and 11, in the case of the above-mentioned antibody (a).

The complementarity determining regions (CDRs) encoded by the DNA having these sequences serve as regions that determine the specificity of the antibody. Sequences encoding the other regions (i.e., constant regions and framework regions) of the antibody may therefore be sequences derived from other antibodies. In this context, “other antibodies” also include antibodies derived from non-human organisms, but are preferably those derived from humans from the viewpoint of reducing adverse reactions. Specifically, in the DNA of the present invention, regions encoding each framework region and each constant region in the heavy and light chains preferably comprise nucleotide sequences encoding corresponding human antibody-derived amino acid sequences.

Further examples of the DNA encoding the antibody of the present invention include a DNA encoding a heavy chain variable region comprising a nucleotide sequence encoding the amino acid sequence of SEQ ID NO: 8, and a DNA encoding a light chain variable region comprising a nucleotide sequence encoding the amino acid sequence of SEQ ID NO: 12. In this context, the nucleotide sequence encoding the amino acid sequence of SEQ ID NO: 8 is, for example, the nucleotide sequence of SEQ ID NO: 13. An example of nucleotide sequences encoding the amino acid sequence of SEQ ID NO: 12 is the nucleotide sequence of SEQ ID NO: 14. When such a DNA comprises regions encoding constant regions of the heavy and light chains, each of the regions preferably comprises a nucleotide sequence encoding a corresponding human antibody-derived amino acid sequence (amino acid sequence of each constant region of the heavy and light chains).

These antibody DNAs can be obtained, for example, by the methods described above, or the following method. First, total RNAs are prepared from hybridomas producing the antibody of the present invention using a commercially available RNA extraction kit, and cDNAs are synthesized therefrom using reverse transcriptase and random primers or the like. Subsequently, the antibody-encoding cDNAs are amplified by PCR using oligonucleotide primers for conserved sequences of variable regions in known mouse antibody heavy or light chain genes. Sequences encoding the constant regions can be obtained by PCR amplification of the known sequences. The nucleotide sequence of the DNA can be incorporated into a plasmid or a phage for sequencing, for example, and determined according to a conventional method.

The present invention further provides the following polypeptides and DNAs related to the above-mentioned antibody (a):

(i) a polypeptide comprising any of amino acid sequences of SEQ ID NOs: 8 and 12, and a DNA encoding the polypeptide (e.g., a DNA comprising any of the nucleotide sequences of SEQ ID NOs: 13 and 14);

(ii) heavy chain CDR polypeptides selected from the group consisting of amino acid sequences shown by SEQ ID NOs: 5, 6, and 7, and a DNA encoding the polypeptides; and

(iii) light chain CDR polypeptides selected from amino acid sequences shown by SEQ ID NOs: 9, 10, and 11, and a DNA encoding the polypeptides.

These polypeptides and DNAs can be prepared using genetic engineering techniques as described above.

<Summary of the Present Invention>

The aspects of the present invention described above are summarized below.

(1) An antibody or a fragment thereof, wherein the antibody or the fragment thereof have immunological reactivity with a CAPRIN-1 protein and comprise a heavy chain variable region comprising complementarity determining regions of SEQ ID NOs: 5, 6, and 7 and a light chain variable region comprising complementarity determining regions of SEQ ID NOs: 9, 10, and 11.

(2) The antibody or the fragment thereof according to (1), wherein the antibody is a human antibody, a humanized antibody, a chimeric antibody, a single-chain antibody, or a multispecific antibody.

(3) The antibody or the fragment thereof according to (1) or (2), wherein the antibody or the fragment thereof is conjugated with an antitumor agent.

(4) A pharmaceutical composition for treatment and/or prevention of cancer, comprising the antibody or the fragment thereof according to any of (1) to (3) as an active ingredient.

(5) The pharmaceutical composition according to (4), wherein the cancer is breast cancer, kidney cancer, pancreatic cancer, colorectal cancer, lung cancer, brain tumor, gastric cancer, uterine cervix cancer, ovary cancer, prostate cancer, urinary bladder cancer, esophageal cancer, leukemia, lymphoma, fibrosarcoma, mastocytoma, or melanoma.

(6) A pharmaceutical combination for treatment and/or prevention of cancer, comprising the pharmaceutical composition according to (4) or (5) and a pharmaceutical composition comprising an antitumor agent.

(7) A DNA encoding the antibody or the fragment thereof according to (1) or (2).

(8) A method for treating and/or preventing cancer, comprising administering the antibody or the fragment thereof according to any of (1) to (3), the pharmaceutical composition according to (4) or (5), or the pharmaceutical combination according to (6), to a subject.

EXAMPLES

Hereinafter, the present invention will be described specifically with reference to Examples. However, the scope of the present invention is not intended to be limited by these specific examples.

Example 1 Analysis of CAPRIN-1 Expression in Each Tissue

CAPRIN-1 gene expression in canine and human normal tissues and various cell lines was examined by RT-PCR according to Example 1(4) of WO2010/016526. As a result, strong expression was observed in the testis among the healthy canine tissues, whereas expression was observed in canine breast cancer and adenocarcinoma tissues. Further, as a result of examining the expression in human tissues, the expression was observed only in the testis among normal tissues, as with the canine CAPRIN-1 gene. By contrast, the expression was detected in many types of cancer cell lines, including 8 human breast cancer cell lines (ZR75-1, MCF7, T47D, SK-BR-3, MDA-MB-157, BT-20, MDA-MB-231V, and MRK-nu-1) and 4 pancreatic cancer cell lines (Capan-2, MIAPaCa-2, Panc-1, and BxPc-3), among cancer cells. These results demonstrated that CAPRIN-1 expression is not found in normal tissues other than the testis, whereas CAPRIN-1 is expressed in the breast cancer cell lines.

Example 2 Preparation of Mouse Monoclonal Antibody Against CAPRIN-1

100 μg of human CAPRIN-1 proteins (having the amino acid sequence of SEQ ID NO: 2) prepared in Example 3 of WO2010/016526 was mixed with an equal amount of MPL+TDM adjuvant (Sigma-Aldrich Corp.). This mixture was used as an antigen solution per mouse. The antigen solution was intraperitoneally administered to each 6-week-old Balb/c mouse (prepared by Japan SLC, Inc.). Then, 7 administrations were performed every 1 week to complete immunization. Three days after the final immunization, the spleen of each mouse was excised and ground between two sterilized glass slides. Procedures of washing with PBS(−) (manufactured by Nissui Pharmaceutical Co., Ltd.) and centrifuging at 1500 rpm for 10 minutes to remove the supernatant were repeated three times to obtain spleen cells. The obtained spleen cells were mixed with mouse myeloma cells SP2/0 (purchased from ATCC) at a ratio of 10:1. A PEG solution prepared by mixing 200 μl of an RPMI1640 medium containing 10% FBS, which was heated to 37° C., with 800 μl of PEG1500 (manufactured by Boehringer Ingelheim GmbH) was added to the cell mixture, and then it was left to stand for 5 minutes for cell fusion. After removal of the supernatant via centrifugation at 1700 rpm for 5 minutes, the cells were suspended in 150 ml of an RPMI1640 medium containing 15% FBS supplemented with 2% equivalent of a HAT solution (Gibco) (HAT selective medium). This suspension was seeded onto fifteen 96-well plates (Nunc) at 100 μl/well. The spleen cells and the myeloma cells were fused by culturing for 7 days at 37° C., 5% CO₂ to obtain hybridomas.

The prepared hybridomas were screened for the binding affinity of antibodies produced by the hybridomas against CAPRIN-1 proteins as an indicator. A 1 μg/ml solution of the CAPRIN-1 protein prepared in Example 3 of WO2010/016526 was added to a 96-well plate at 100 μl/well and left to stand at 4° C. for 18 hours. Each well was washed three times with PBS-T. Then, a 0.5% bovine serum albumin (BSA) solution (manufactured by Sigma-Aldrich Corp.) was added thereto at 400 μl/well and left to stand at room temperature for 3 hours. The solution in each well was removed, and each well was washed three times with 400 μl of PBS-T. Then, the culture supernatant of each hybridoma obtained above was added thereto at 100 μl/well and left to stand at room temperature for 2 hours. Each well was washed three times with PBS-T. Then, HRP-labeled anti-mouse IgG (H+L) antibodies (manufactured by Invitrogen Corp.) diluted 5000-fold with PBS were added thereto at 100 μl/well and left to stand at room temperature for 1 hour. Each well was washed three times with PBS-T. Then, a TMB substrate solution (manufactured by Thermo Fisher Scientific Inc.) was added thereto at 100 μl/well and left to stand for 15 to 30 minutes to cause color reaction. After the color development, the reaction was terminated by the addition of 1N sulfuric acid at 100 μl/well. The absorbance was measured at 450 nm and 595 nm using an absorption spectrometer. As a result, several hybridomas producing antibodies having high absorbance were selected.

The selected hybridomas were added to a 96-well plate at 0.5 cells/well and cultured in the plate. One week later, hybridomas forming single colonies in the wells were observed. The cells in these wells were further cultured, and the cloned hybridomas were screened for the binding affinity of antibodies produced by the hybridomas to the CAPRIN-1 protein as an indicator. A 1 μg/ml solution of the CAPRIN-1 protein prepared in Example 3 of WO2010/016526 was added to a 96-well plate at 100 μl/well and left to stand at 4° C. for 18 hours. Each well was washed three times with PBS-T. Then, a 0.5% BSA solution was added thereto at 400 μl/well and left to stand at room temperature for 3 hours. The solution in each well was removed, and each well was washed three times with 400 μl of PBS-T. Then, the culture supernatant of each hybridoma obtained above was added thereto at 100 μl/well and left to stand at room temperature for 2 hours. Each well was washed three times with PBS-T. Then, HRP-labeled anti-mouse IgG (H+L) antibodies (manufactured by Invitrogen Corp.) diluted 5000-fold with PBS were added thereto at 100 μl/well and left to stand at room temperature for 1 hour. Each well was washed three times with PBS-T. Then, a TMB substrate solution (manufactured by Thermo Fisher Scientific Inc.) was added thereto at 100 μl/well and left to stand for 15 to 30 minutes to cause color reaction. After the color development, the reaction was terminated by the addition of 1 N sulfuric acid at 100 μl/well. The absorbance was measured at 450 nm and 595 nm using an absorption spectrometer. As a result, 112 hybridoma lines producing monoclonal antibodies reactive with the CAPRIN-1 protein were obtained.

Next, these monoclonal antibodies were screened for antibodies reactive with the surface of breast cancer cells expressing CAPRIN-1. Specifically, 10⁶ cells of a human breast cancer cell line MDA-MB-231V were centrifuged in a 1.5-ml microcentrifuge tube. 100 μl of the culture supernatant of the hybridoma obtained above was added thereto and left to stand for 1 hour on ice. After washing with PBS, FITC-labeled goat anti-mouse IgG antibodies (manufactured by Invitrogen Corp.) diluted 500-fold with PBS containing 0.1% FBS were added thereto and left to stand for 1 hour on ice. After washing with PBS, the fluorescence intensity was measured using FACSCalibur (Becton, Dickinson and Company). On the other hand, the same operation as above was performed using the serum of each untreated 6-week-old Balb/c mouse diluted 500-fold with a medium for hybridoma culture, instead of the antibodies, to prepare a control. As a result, one monoclonal antibody (#1) having stronger fluorescence intensity than that of the control, i.e., reactive with the surface of the breast cancer cells, was selected.

Example 3 Characterization of Selected Monoclonal Antibody

Amplification fragments of genes encoding the variable regions of the monoclonal antibodies obtained in Example 2 were obtained according to a method described in Example 5 of WO2010/016526 and analyzed for their gene sequences and amino acid sequences encoded thereby. As a result, the monoclonal antibody #1 had variable regions consisting of the heavy chain variable region of SEQ ID NO: 8 and the light chain variable region of SEQ ID NO: 12. The gene sequence encoding the heavy chain variable region of the obtained monoclonal antibody #1 is shown in SEQ ID NO: 13, and the amino acid sequence is shown in SEQ ID NO: 8. The gene sequence encoding the light chain variable region of the obtained monoclonal antibody #1 is shown in SEQ ID NO: 14, and the amino acid sequence is shown in SEQ ID NO: 12.

In other words, the monoclonal antibody #1 was found to comprise the heavy chain variable region of SEQ ID NO: 8 and the light chain variable region of SEQ ID NO: 12, wherein the heavy chain variable region had CDR1, CDR2, and CDR3 consisting of the amino acid sequences of SEQ ID NOs: 5, 6, and 7, respectively, and the light chain variable region had CDR1, CDR2, and CDR3 consisting of the amino acid sequences of SEQ ID NOs: 9, 10, and 11, respectively.

Example 4 Preparation of Human-Mouse Chimeric Monoclonal Antibody

The gene amplification fragment prepared in Example 3 comprising the sequence (SEQ ID NO: 13) of the heavy chain variable region of the mouse monoclonal antibody #1 was treated at both ends with a restriction enzyme, then purified, and inserted according to a conventional method into a vector pcDNA4/myc-His (manufactured by Invitrogen Corp.) already having gene inserts of a mouse antibody-derived leader sequence and a human IgG₁ H chain constant region comprising the amino acid sequence of SEQ ID NO: 37. Also, the gene amplification fragment comprising the sequence (SEQ ID NO: 14) of the light chain variable region of the mouse monoclonal antibody #1 was treated at both ends with a restriction enzyme, then purified, and inserted according to a conventional method into a vector pcDNA3.1/myc-His (manufactured by Invitrogen Corp.) already having gene inserts of a mouse antibody-derived leader sequence and a human IgG₁ L chain constant region comprising the amino acid sequence of SEQ ID NO: 38.

Next, the recombinant vector having the insert of the heavy chain variable region (SEQ ID NO: 13) of the mouse monoclonal antibody #1 and the recombinant vector having the insert of the light chain variable region (SEQ ID NO: 14) of the mouse monoclonal antibody #1 were introduced into CHO-K1 cells (obtained from Riken Cell Bank). Specifically, 2×10⁵ CHO-K1 cells were cultured in a Ham's F12 medium (manufactured by Invitrogen Corp.) containing 1 ml of 10% FBS per well in a 12-well culture plate, and washed with PBS(−). Then, a fresh Ham's F12 medium containing 1 ml of 10% FBS per well was added thereto. 250 ng each of the vectors in 30 μl of OptiMEM (manufactured by Invitrogen Corp.) was mixed with 30 μl of Polyfect transfection reagent (manufactured by Qiagen N.V.), and this mixture was added to each well. The CHO-K1 cells cotransfected with the recombinant vectors were cultured in a Ham's F12 medium containing 10% FBS supplemented with 200 μg/ml Zeocin (manufactured by Invitrogen Corp.) and 200 μg/ml Geneticin (manufactured by Roche Diagnostics K.K.) and then seeded onto a 96-well plate at 0.5 cells/well to prepare a cell line stably producing a human-mouse chimeric monoclonal antibody #1 (#1) having the variable regions of the mouse monoclonal antibody #1.

Each prepared cell line was cultured for 5 days in a 150-cm² flask at 5×10⁵ cells/ml in 30 ml of a serum-free OptiCHO medium (manufactured by Invitrogen Corp.) to obtain culture supernatants containing the human-mouse chimeric monoclonal antibody #1.

Also, cell lines stably producing human-mouse chimeric comparative monoclonal antibodies 1 to 11 were prepared in the same way as above respectively, on the basis of the following anti-CAPRIN-1 mouse-derived monoclonal antibodies disclosed in WO2010/016526 as comparative antibodies: a comparative antibody 1 having the heavy chain variable region of SEQ ID NO: 15 and the light chain variable region of SEQ ID NO: 16; a comparative antibody 2 having the heavy chain variable region of SEQ ID NO: 17 and the light chain variable region of SEQ ID NO: 18; a comparative antibody 3 having the heavy chain variable region of SEQ ID NO: 19 and the light chain variable region of SEQ ID NO: 20; a comparative antibody 4 having the heavy chain variable region of SEQ ID NO: 21 and the light chain variable region of SEQ ID NO: 22; a comparative antibody 5 having the heavy chain variable region of SEQ ID NO: 23 and the light chain variable region of SEQ ID NO: 24; a comparative antibody 6 having the heavy chain variable region of SEQ ID NO: 25 and the light chain variable region of SEQ ID NO: 26; a comparative antibody 7 having the heavy chain variable region of SEQ ID NO: 27 and the light chain variable region of SEQ ID NO: 28; a comparative antibody 8 having the heavy chain variable region of SEQ ID NO: 29 and the light chain variable region of SEQ ID NO: 30; a comparative antibody 9 having the heavy chain variable region of SEQ ID NO: 31 and the light chain variable region of SEQ ID NO: 32; a comparative antibody 10 having the heavy chain variable region of SEQ ID NO: 33 and the light chain variable region of SEQ ID NO: 34; and a comparative antibody 11 having the heavy chain variable region of SEQ ID NO: 35 and the light chain variable region of SEQ ID NO: 36. Each prepared cell line was cultured for 5 days in a 150-cm² flask at 5×10⁵ cells/ml in 30 ml of a serum-free OptiCHO medium (manufactured by Invitrogen Corp.) to obtain culture supernatants containing respective human-mouse chimeric comparative antibodies 1 to 11.

Example 5 Expression Analysis of CAPRIN-1 on Surface of Various Cancer Cells Using anti-CAPRIN-1 antibody #1

Next, the human breast cancer cell lines (ZR75-1, MCF7, T47D, SK-BR-3, MDA-MB-157, BT-20, MDA-MB-231V, and MRK-nu-1), the kidney cancer cell lines (Caki-1, Caki-2, A498, and ACHN), the urinary bladder cancer cell line (T24), the ovary cancer cell line (SKOV3), the lung cancer cell lines (QG56 and A549), the pancreatic cancer cell lines (Capan-2 and MIAPaCa-2), the prostate cancer cell line (PC3), the uterine cervix cancer cell line (SW756), the fibrosarcoma cell line (HT1080), the brain tumor cell lines (T98G, U87MG, U251, SNB19, and U373), the gastric cancer cell lines (MNK28 and MNK45), the colorectal cancer cell lines (HT29, Lovo, CaCo2, SW480, and HCT116), the leukemia cell line (AML5), and the lymphoma cell line (Ramos) observed to have CAPRIN-1 gene expression were examined for their expression of CAPRIN-1 proteins on the cell surface using the culture supernatants containing #1 obtained in Example 2. 5×10⁵ cells of each cell line were centrifuged in each 1.5-ml microcentrifuge tube. A culture supernatant (100 μl) containing the antibody #1 was added to the tube and left to stand for 1 hour on ice. After washing with PBS, FITC-labeled goat anti-mouse IgG (H+L) antibodies (manufactured by Jackson ImmunoResearch Laboratories, Inc.) diluted with PBS containing 0.1% FBS were added thereto and left to stand at 4° C. for 30 minutes. After washing with PBS, the fluorescence intensity was measured using FACSCalibur (Becton, Dickinson and Company). The negative control used was cells reacted only with secondary antibodies. As a result, the cells treated with the antibody #1 had fluorescence intensity at least 35% stronger than that of the negative control. This demonstrated that CAPRIN-1 proteins are expressed on the cell membrane surface of the human cancer cell lines. The rates of enhancement in the fluorescence intensity was expressed as the rates of increase in mean fluorescence intensity (MFI) in respective cell lines, which are calculated according to the following formula.

Rate of increase in mean fluorescence intensity (Rate of enhancement in fluorescence intensity) (%)=((MFI of cells reacted with the anti-CAPRIN-1 antibodies)−(Control MFI))/(Control MFI)×100

Example 6 Antitumor Effect (ADCC activity) of Anti-CAPRIN-1 Antibody on Cancer Cell

The anti-CAPRIN-1 human-mouse chimeric monoclonal antibody #1 obtained in Example 4 was examined for whether it has an ability to damage CAPRIN-1-expressing cancer cells by determining ADCC activity. The culture supernatant of a cell line producing #1 was purified using Hitrap Protein A Sepharose FF (manufactured by GE Healthcare Bio-Sciences Ltd.). After replacement with PBS(−), the solution was filtered through a 0.22-μm filter (manufactured by Millipore Corp.). The resulting antibody was used for activity assay. 10⁶ cells each of the human breast cancer cell line MCF7, the human colorectal cancer cell line HCT-116, the human pancreatic cancer cell line MIAPaCa-2, the human kidney cancer cell line Caki-2, and the human lung cancer cell line QG56 observed to have CAPRIN-1 expression were collected into a 50-ml centrifuge tube, and 100 μCi of chromium 51 was then added thereto, followed by incubation at 37° C. for 2 hours. Then, the cells were washed three times with an RPMI1640 medium containing 10% FBS and added at 2×10³ cells/well to a 96-well V-bottom plate to prepare target cells. The purified antibody #1 and the human-mouse chimeric comparative antibodies 1 to 11 obtained in Example 4 were each added thereto at 1 μg/well. A cell population containing human NK cells separated using a conventional method from human peripheral blood lymphocytes was added to the plate at 2×10⁵ cells/well and cultured for 4 hours at 37° C., 5% CO₂. After the culture, the amount of chromium 51 released from damaged tumor cells was measured in the culture supernatant to calculate the cytotoxic activity of each anti-CAPRIN-1 antibody against the cancer cells. The negative control used was cells treated with isotype control antibodies. The cell population containing NK cells that was used in this evaluation was prepared as follows: human peripheral blood mononuclear cells separated from peripheral blood according to a conventional method using a specific gravity separation solution Histopaque for human peripheral blood mononuclear cell separation (Sigma-Aldrich Corp.) were reacted with various FITC fluorescent dye-labeled antibodies (anti-human CD3 antibody, anti-human CD20 antibody, anti-human CD19 antibody, anti-human CD11c antibody, and anti-HLA-DR antibody (Becton, and Dickinson and Company)); and a cell population unstained with the antibodies was separated therefrom using a cell sorter (FACS Vantage SE (Becton, and Dickinson and Company)), or a cell population was separated with human NK cell separation kit (manufactured by Miltenyi Biotec K.K.). As a result of evaluating cytotoxic activity against the cancer cells, the isotype control antibodies used and the comparative antibodies 1 to 11 used had cytotoxic activity less than 5% against all of the human breast cancer cell line MCF7, the human colorectal cancer cell line HCT-116, the human pancreatic cancer cell line MIAPaCa-2, the human kidney cancer cell line Caki-2, and the human lung cancer cell line QG56. By contrast, the antibody #1 exhibited cytotoxic activity of 26%, 17%, 29%, 23%, and 11% against the human breast cancer cell line MCF7, the human colorectal cancer cell line HCT-116, the human pancreatic cancer cell line MIAPaCa-2, the human kidney cancer cell line Caki-2, and the human lung cancer cell line QG56, respectively. Likewise, the isotype control antibodies used and the comparative antibodies 1 to 11 used had cytotoxic activity less than 4% against all other cancer cells, breast cancer cell lines ZR75-1, T47D, Hs578T, 8T-20, SK-BR-3, MDA-MB-231V, and MRK-nu-1, glioma cell lines T98G and U373, a lung cancer cell line A549, kidney cancer cell lines Caki-1 and ACHN, a uterine cervix cancer cell line SW756, a urinary bladder cancer cell line T24, gastric cancer cell lines MKN28 and MKN45, a colorectal cancer cell line SW480, a leukemia cell line AML5, and a lymphoma cell line Ramos. By contrast, the antibody #1 was observed to have 10% or higher cytotoxic activity against these cell lines. These results showed that the obtained monoclonal antibody #1 against CAPRIN-1 damages CAPRIN-1-expressing cancer cells through their ADCC activity, and it was demonstrated that the antibody #1 exhibits stronger cytotoxic activity against human cancer cells than that of the comparative antibodies 1 to 11.

These results were obtained via determination of cytotoxic activity by, as described above, mixing the anti-CAPRIN-1 antibody used in the present invention, lymphocytes (cell population containing NK cells), and 2×10³ cells of each cancer cell line with incorporated chromium 51, culturing the cells for 4 hours; after the culture, measuring the amount of chromium 51 released into the medium; and calculating the cytotoxic activity against each cancer cell line according to the following formula*.

*Expression: Cytotoxic activity (%)=[Amount of chromium 51 released from the target cells treated with the antibody against CAPRIN-1 and lymphocytes (cell population containing NK cells)]/[Amount of chromium 51 released from target cells treated with 1 N hydrochloric acid]×100

Next, the human-mouse chimeric monoclonal antibody #1 obtained in Example 4 was evaluated for its antitumor effect in cancer-bearing mice in vivo. The antibody #1 used was column-purified from the culture supernatant of each cell line producing the antibody #1. Similarly, the anti-CAPRIN-1 human-mouse chimeric comparative monoclonal antibodies 1 to 11 prepared in Example 4 were also evaluated for their antitumor effects in cancer-bearing mice in vivo.

Specifically, the antibody #1 was examined for its antitumor effect using cancer-bearing mice in which a CAPRIN-1-expressing human-derived cancer cell line was transplanted. Human pancreatic cancer cell line Capan-2 cells (purchased from ATCC) were subcutaneously transplanted at 2×10⁶ cells per mouse into the backs of 65 Balb/c nude mice (manufactured by Japan SLC, Inc.) and grown until the size of tumor became approximately 5 mm in diameter. The antibody #1 and the human-mouse chimeric comparative antibodies 1 to 11 were each intraperitoneally administered at a dose of 200 μg (200 μl)/mouse to 5 animals (per antibody) of the cancer-bearing mouse. Then, each antibody was intraperitoneally administered to the cancer-bearing mice at the same dose as above a total of three times for 2 days. The size of tumor was measured every day to assay the antitumor effect. On the other hand, PBS(−) was administered instead of the antibodies to the remaining 5 animals of the cancer-bearing mouse, as a control group. The size of tumor (volume) was calculated according to the formula: 0.5×(Major axis×Minor axis×Minor axis).

As a result of assay of the antitumor effect, in the test group that received the antibody #1 against CAPRIN-1, tumor growth was suppressed to 68% at day 29 after the antibody administration relative to the control group in terms of tumor size at the same date (defined as 100%). By contrast, in the mice that received the human-mouse chimeric comparative antibodies 1 to 11, tumor growth was suppressed to approximately 85%. These results demonstrated that the obtained anti-CAPRIN-1 antibody #1 exerts in vivo an antitumor effect on CAPRIN-1-expressing cancer cells. The results also demonstrated that the antibody #1 exerts in vivo a stronger antitumor effect than that of the comparative antibodies 1 to 11.

Example 7 The Number of CAPRIN-1 Molecules on Surface of Various Cancer Cells Recognized by Anti-CAPRIN-1 Antibody #1

Human breast cancer cell lines (ZR75-1, MCF7, T47D, SK-BR-3, MDA-MB-157, BT-20, MDA-MB-231V, and MRK-nu-1), kidney cancer cell lines (Caki-1, Caki-2, A498, and ACHN), a urinary bladder cancer cell line (T24), an ovary cancer cell line (SKOV3), lung cancer cell lines (QG56 and A549), pancreatic cancer cell lines (MIAPaCa-2 and Capan-2), a prostate cancer cell line (PC3), a uterine cervix cancer cell line (SW756), a fibrosarcoma cell line (HT1080), brain tumor cell lines (T98G, U87MG, U251, SNB19, and U373), gastric cancer cell lines (MNK28 and MNK45), colorectal cancer cell lines (HT29, Lovo, CaCo2, SW480, and HCT116), a leukemia cell line (AML5), and a lymphoma cell line (Ramos) were examined using QIFIKIT, an assay kit for the number of molecules (manufactured by Dako Japan Inc.) for the number of CAPRIN-1 molecules on their cell surface recognized by the anti-CAPRIN-1 antibody #1. Similarly, the number of CAPRIN-1 molecules on the surface of these various cancer cells was also examined using the comparative antibodies 1 to 11, which are anti-CAPRIN-1 monoclonal antibodies prepared in Example 4.

According to the protocol attached to the kit, the antibody #1 and comparative antibodies 1 to 11 were diluted into 5 μg/ml at final concentration with PBS, and this dilution was added to each cell line and reacted for 30 minutes. After washing with PBS, fluorescently labeled anti-mouse IgG antibodies attached to the kit were added as secondary antibodies, together with calibration beads attached to the kit, to each cell line and left to stand for 45 minutes on ice. Each cell line and the calibration beads were washed with PBS. Then, the fluorescence intensity was measured using FACSCalibur (Becton, Dickinson and Company) to obtain a mean fluorescence intensity value (mean). Further, the fluorescence intensity was also measured using comparative antibodies similarly as above to obtain a mean. The negative control used was cells reacted with isotype control antibodies, and a mean was also obtained. Each mean fluorescence intensity value (mean) was used to calculate the number of molecules according to the protocol attached to the kit. As a result, the number of CAPRIN-1 molecules on the surface of various cancer cells recognized by the antibody #1 was 10⁵ or more per cell for all the examined human cancer cell lines. On the other hand, the number of molecules recognized by the comparative monoclonal antibodies 1 to 11 was less than 10⁵ per cell.

INDUSTRIAL APPLICABILITY

The antibody of the present invention is useful in the treatment and/or prevention of cancer.

All publications, patents, and patent applications cited herein are incorporated herein by reference in their entirety. 

1. An antibody or a fragment thereof, wherein the antibody or the fragment thereof have immunological reactivity with a CAPRIN-1 protein and comprise a heavy chain variable region comprising complementarity determining regions of SEQ ID NOs: 5, 6, and 7 and a light chain variable region comprising complementarity determining regions of SEQ ID NOs: 9, 10, and
 11. 2. The antibody or the fragment thereof according to claim 1, wherein the antibody is a human antibody, a humanized antibody, a chimeric antibody, a single-chain antibody, or a multispecific antibody.
 3. The antibody or the fragment thereof according to claim 1, wherein the antibody or the fragment thereof is conjugated with an antitumor agent.
 4. A pharmaceutical composition for treatment and/or prevention of cancer, comprising the antibody or the fragment thereof according to claim 1 as an active ingredient.
 5. The pharmaceutical composition according to claim 4, wherein the cancer is breast cancer, kidney cancer, pancreatic cancer, colorectal cancer, lung cancer, brain tumor, gastric cancer, uterine cervix cancer, ovary cancer, prostate cancer, urinary bladder cancer, esophageal cancer, leukemia, lymphoma, fibrosarcoma, mastocytoma, or melanoma.
 6. A pharmaceutical combination for treatment and/or prevention of cancer, comprising the pharmaceutical composition according to claim 4 and a pharmaceutical composition comprising an antitumor agent.
 7. A DNA encoding the antibody or the fragment thereof according to claim
 1. 8. A method for treating and/or preventing cancer, comprising administering the antibody or the fragment thereof according to claim 1, to a subject.
 9. The antibody or the fragment thereof according to claim 2, wherein the antibody or the fragment thereof is conjugated with an antitumor agent.
 10. A pharmaceutical composition for treatment and/or prevention of cancer, comprising the antibody or the fragment thereof according to claim 2 as an active ingredient.
 11. A pharmaceutical composition for treatment and/or prevention of cancer, comprising the antibody or the fragment thereof according to claim 3 as an active ingredient.
 12. A pharmaceutical combination for treatment and/or prevention of cancer, comprising the pharmaceutical composition according to claim 5 and a pharmaceutical composition comprising an antitumor agent.
 13. A DNA encoding the antibody or the fragment thereof according to claim
 2. 14. A method for treating and/or preventing cancer, comprising administering the pharmaceutical composition according to claim 4, to a subject.
 15. A method for treating and/or preventing cancer, comprising administering the pharmaceutical combination according to claim 6, to a subject. 